In reciprocating piston engines, vibrational forces are produced due to the movement and mass of reciprocating parts. To offset such vibrational forces, engines are often equipped with balance shafts, which include balancing weights. Such balancing weights act to counterbalance and offset vibrational forces produced by reciprocal parts during the operation of the engine. Typical reciprocal engines often utilize pairs of balance shafts. Such pairs of balance shafts are supported on casings disposed in an oil pan below the engine cylinder block. The balance shafts are linked to each other and a to an engine crankshaft to transfer the rotational forces from the crankshaft to the balance shafts. Balance shafts are typically linked to the crankshaft via a chain, belt, or the like, such that the balance shafts rotate at twice the rotational speed and in the opposite direction of the crankshaft. The resultant vibrational forces of the balance shafts counterbalance and offset the vibrational forces of the engine.
In general, such balance shafts are supported at a plurality of positions to secure the balance shafts to the engine. Since a substantial amount of balancing torque is produced when the balance shafts rotate, the shafts must be supported by a sufficiently rigid bearing structure to remain secured to the engine during operation of the engine. Typically, balance shafts are supported and secured by bearing caps having journal portions designed to capture a portion of the balance shaft. Bearing caps known in the art are generally solid bodies fabricated from cast iron and split into upper and lower halves, as disclosed in U.S. Pat. No. 5,535,643.
As is known in the art, one method of increasing the strength of the journal portion is to manufacture bearing caps from billet steel or other such rigid material through a casting or machining process. Secondary operations often accompany such processes, such as the drilling of journal portions through the cast or machined bearing cap. The journal portions are drilled to accommodate the insertion of the balance shafts into the journal portions.
There is a constant need in the art to reduce the weight of automotive components, increase the strength and machinability of such components, and reduce costs. Any such improvements are constantly sought in the automotive industry.